Hamilton, who has accused the seven-time Tour de France winner of doping, and Armstrong had a conversation in an Aspen, Colo., restaurant Saturday night. Attorney Chris Manderson said Hamilton told him Armstrong made derisive comments, while the restaurant co-owner and friend of Armstrong told ESPN.com: "It was not a big confrontation."

Federal officials are now in their second year of investigating doping in cycling. A Los Angeles-based grand jury is hearing evidence that could lead to charges of fraud, conspiracy and drug trafficking against Armstrong and his team.

"Lance Armstrong is a possible defendant in an investigation that's been widely reported, and Tyler is a probable witness," Manderson told the website. "When there's any contact, especially aggressive contact, we as lawyers have a duty to inform the authorities. ... What they will do with it, I don't know."

A spokesman for Armstrong declined comment when approached by ESPN.com. Armstrong told Outside Magazine the incident was "certainly awkward for both of us" and "truly uneventful."